To the device itself: had this installed by a specialist company, namely in exchange for an existing hydraulically controlled instantaneous water heaters Vaillant. Everything went smoothly - the effort was only just under 25 minutes and what was incurred on "dirt" was not worth mentioning and could be wiped off with a damp cloth.
After a good week use, I wonder why I did not make this exchange ten years ago ...
No more cold showers because the water pressure drops and the (old) unit turns off, no more scalding because the large heat setting switches on after one has in the meantime the tap further turned a little and suddenly the water pressure increases again.
This is now all water under the bridge - by the electronic control, I now always even warm water, no matter how much water comes out of the tap. In addition, the temperature can be very finely adjusted. Another positive effect is that the water again reaches the preset temperature very quickly if you have left it in the shower while soaping (no splash of cold water, as was the rule at the hydraulically controlled instantaneous water heaters - especially in winter).
Conclusion: absolutely recommendable device, significant gain in comfort, water and energy efficient - and for relatively little money.
Small downside (at least in my case and not the product itself causes): It might be difficult to find a specialist who relents to take over the installation. With me was only the fifth willing the fours before just wanted to spoil something that they had sold themselves ...
Sincerely
Jazzy 42